Parametric analysis using the finite element method to investigate prosthetic interface stresses for persons with below-knee amputation

A finite element (FE) model of the below-knee residual limb and prosthetic socket was created to investigate the effects of parameter variations on the interface stress distribution during static stance . This model was based upon geometric approximations of anthropometric residual limb geometry . The model was not specific to an individual with amputation, but could be scaled to approximate the limb of a particular subject . Parametric analyses were conducted to investigate the effects of prosthetic socket design and residual limb geometry on the residual limb/prosthetic socket interface stresses . Behavioral trends were illustrated via sensitivity analysis. The results of the parametric analyses indicate that the residual limb/prosthetic socket interface stresses are affected by variations in both prosthetic design and residual limb geometry . Specifically, the analyses indicate : 1) the residual limb/prosthetic liner interface pressures are relatively insensitive to the socket stiffness ; 2) the stiffness of the prosthetic liner influences the interface stress distribution for both the unrectified and patellar-tendon-bearing (PTB) rectified models--the external load state appears to influence the interface pressure distribution, while the prosthetic socket rectification appears to influence the interface shear stress distribution ; 3) the interface pressures are very sensitive to the prosthetic rectification ; 4) the shape and relative bulk of soft tissue may This material is based upon work supported by the National Institute on Disability and Rehabilitation Research (NIDRR), U .S . Department of Education, and the Department of Veterans Affairs, Rehabilitation Research and Development Service, Washington, DC 20420. Address all correspondence and requests for reprints to : M. Barbara Silver-Thorn, PhD, Marquette University, Department of Biomedical Engineering . Olin Building, Room 301, P .O . Box 1881, Milwaukee, WI 53201-1881 ; email : [email protected] .mu .edu significantly influence the interface pressure distribution ; 5) the interface pressure distribution is also influenced by the residual limb length; and 6) the stiffness/compliance of the residual limb soft tissues may significantly alter the interface pressure distribution.